Remove race conditions from UncertaintyGroup

utility/uncertaintygroup.go

@@ -15,6 +15,7 @@ package utility
 
 import (
 	"fmt"
+	"sync"
 )
 
 type state int
@@ -62,18 +63,19 @@ type uncertaintyGroup struct {
 	successes uint
 	results   chan error
 	anomalies []error
+	sync.Mutex
 }
 
-func (g uncertaintyGroup) Succeed() {
-	if g.state == finished {
+func (g *uncertaintyGroup) Succeed() {
+	if g.isFinished() {
 		panic("cannot remark when done")
 	}
 
 	g.results <- nil
 }
 
-func (g uncertaintyGroup) Fail(err error) {
-	if g.state == finished {
+func (g *uncertaintyGroup) Fail(err error) {
+	if g.isFinished() {
 		panic("cannot remark when done")
 	}
 
@@ -84,22 +86,42 @@ func (g uncertaintyGroup) Fail(err error) {
 	g.results <- err
 }
 
-func (g uncertaintyGroup) MayFail(err error) {
-	if g.state == finished {
+func (g *uncertaintyGroup) MayFail(err error) {
+	if g.isFinished() {
 		panic("cannot remark when done")
 	}
 
 	g.results <- err
 }
 
-func (g *uncertaintyGroup) Wait() bool {
+func (g *uncertaintyGroup) isFinished() bool {
+	g.Lock()
+	defer g.Unlock()
+
+	return g.state == finished
+}
+
+func (g *uncertaintyGroup) finish() {
+	g.Lock()
+	defer g.Unlock()
+
+	g.state = finished
+}
+
+func (g *uncertaintyGroup) start() {
+	g.Lock()
+	defer g.Unlock()
+
 	if g.state != unstarted {
 		panic("cannot restart")
 	}
 
-	defer close(g.results)
-
 	g.state = started
+}
+
+func (g *uncertaintyGroup) Wait() bool {
+	defer close(g.results)
+	g.start()
 
 	for g.remaining > 0 {
 		result := <-g.results
@@ -113,12 +135,12 @@ func (g *uncertaintyGroup) Wait() bool {
 		g.remaining--
 	}
 
-	g.state = finished
+	g.finish()
 
 	return len(g.anomalies) == 0
 }
 
-func (g uncertaintyGroup) Errors() []error {
+func (g *uncertaintyGroup) Errors() []error {
 	if g.state != finished {
 		panic("cannot provide errors until finished")
 	}
@@ -126,7 +148,7 @@ func (g uncertaintyGroup) Errors() []error {
 	return g.anomalies
 }
 
-func (g uncertaintyGroup) String() string {
+func (g *uncertaintyGroup) String() string {
 	return fmt.Sprintf("UncertaintyGroup %s with %s failures", g.state, g.anomalies)
 }